Many hormone secretion and tissue responses to hormones that depend on cell membrane receptor transduction are blunted in old animals when compared to young animals. Such changes in hormonal responses are frequently associated with alterations in the levels or ratios of stimulato GTP-binding proteins (Gs) and inhibitory GTP binding proteins (Gi ) which mediate many membrane-bound receptor responses intracellularly. We have been (1) conducting investigations of the effects of aging on the G-protein components of cyclase mediated catecholamines receptors in fat cell and hepatic cell membranes, and (2) studying the effects of aging on responses of EF-1alpha, a G protein which is a key mediator of peptide elongation at the ribosome s to growth hormone and testosterone in skeletal muscle and other tissues. This year, we have devised and validated Western blot assay for determining the quantity of EF-1 in tissue from hormone deficient and hormone treated animals of various ages and have developed an expression vector for EF-1alpha in order to produce a pure EF-1alpha standard.